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Return of the dinosaur (hunters)

Paleontologists continue 20-year recovery of carnivore, discover new fossils

 

Paleontologists working on a high peak in the central Transantarctic Mountains have recovered more than half of the fossils belonging to the first dinosaur found in Antarctica — 20 years after its initial discovery.

And the unearthing of yet two new Early Jurassic dinosaur species near the top of 4,528-meter-high Mount Kirkpatrick promises to keep scientists busy for years to come preparing and describing the important finds.

William Hammer, a professor at Augustana College, led the team that discovered Cryolophosaurus, a nearly 7-meter-long carnivore two decades ago while working from a field camp near the Beardmore Glacier.

“In 90-91, we didn’t know what we had except that it had to be entirely new because it was the first dinosaur,” said Hammer, who returned to the Beardmore region for a third time with his largest team to date in an effort to recover as much of the meat-eating dinosaur as possible.

“It will be one of the most, if not the most, complete predator from the Early Jurassic that we have. It will be quite an impressive specimen,” said Peter Makovicky, curator at the Field Museum, where Cryolophosaurus will eventually reside.

Among the new discoveries is the partial skeleton of an ornithischian, or bird-hipped dinosaur, found under an overhang near the Cryolophosaurus quarry by Roger Smith in the waning days of the field season.

The ornithischia, an extinct herbivore, gets its name from its bird-like hip structure, though birds did not descend from this particular order of dinosaurs. The order includes the genus of the well-known stegosaurus, which emerged in the late Jurassic. Like Cryolophosaurus, the ornithischian specimen also dates to the Early Jurassic, about 200 to 175 million years ago.

In addition, bits of a pelvis bone belonging to a dinosaur in the order saurischia (lizard-hipped) from the Early Jurassic were found quite by accident when loose pieces rolled downhill by one of the team members. The remainder of the hip bone was excavated a few days later.

Making his first trip to the Antarctic, Makovicky said there are few places in the world where paleontologists can expect to recover such early remains of dinosaurs.

“It’s not a well-represented time slice in terms of diversity, especially compared to the Late Cretaceous, which is much better known for its dinosaur diversity around the world,” he said, referring to a time period between 100 and 65 million years ago when dinosaurs were enjoying great success — before their sudden extinction at the end of the Cretaceous.

Makovicky said such a complete, early skeleton becomes invaluable for studying other specimens — a sort of paleontological Rosetta Stone.

“That specimen becomes key, or a guiding specimen, for interpreting the anatomy of more fragmentary dinosaurs we may have from elsewhere,” he explained. “That’s why digging up every possible bone becomes very critical.”

The opportunity to work on the Cryolophosaurus excavation enticed Philip Currie to join the expedition to Antarctica. One of the world’s leading paleontologists, from the University of Alberta, Currie’s interests include carnivorous dinosaurs like the famous Tyrannosaurus rex.

“If you’re interested in the evolution and relationships of dinosaurs, then you pretty much have to look at the early dinosaurs as well,” Currie said.

Currie often works at Dinosaur Provincial Park in Alberta, a treasure trove of Cretaceous dinosaur species. Its high latitude position at the time — about 5 degrees farther north than today — suggests dinosaurs weren’t adverse to cold conditions, Currie said. He sees some parallels between the two polar sites, though migratory patterns would have been more limited in Antarctica.

That’s in contrast to the Early Jurassic, when the world’s landmasses were sealed together in the supercontinent called Pangaea.

“The world was a biogeographic superhighway,” Makovicky said, explaining that an animal could literally traverse from one end of the world to the other.

The big question: Did they? Cryolophosaurus’ closest relatives to date lived in what is modern-day United States and China. In the Pangaea configuration, they would have been at the far corners of the supercontinent from Antarctica.

On the other hand, another find from the same quarry on Mount Kirkpatrick during the 1990-91 season — described less than four years ago in the online journal Acta Palaeontologica Poloncica — appears to be a more southern-bound species.

That creature was a massive plant-eating primitive sauropodomorph, which was called Glacialisaurus hammeri. It also lived during the Early Jurassic about 190 million years ago. The description of the dinosaur was based on partial foot, leg and anklebones. Many more bones of the animal were collected during this season. Sauropodomorph dinosaurs were the largest animals to walk the Earth.

“That [quarry] keeps producing more and more bones,” Hammer said.

However, the field season wasn’t all about dinosaurs this time around. Other members of the team, led by Christian Sidor from the University of Washington, focused on recovering fossils from Triassic sediment, dating between 250 and 200 million years ago.

“We’re trying to do the whole Mesozoic as much as we can,” said Hammer, referring to an era nearly 200 million years long, sandwiched between two mass extinctions, and loosely known as the Age of Dinosaurs.

Palynologist Eva Koppelhus, also from the University of Alberta, was brought onboard to help reconstruct the flora of the Early Jurassic, details of which have been sparse until now. Koppelhus collects rock samples from the outcrops that she believes might contain bits of organic plant material, such as pollen or spores. Such paleobotanical investigations can reveal clues about the past climate.

“This part of Antarctica has never found to have this kind [of material],” Koppelhus said.

That’s in contrast to the Triassic, a period before the Jurassic, which has yielded a rich record of ancient flora.

“It’s simply two different environments; that is the reason why you can find so much in the Triassic and so little in the Lower Jurassic,” Koppelhus said.

The Kirkpatrick dinosaur quarry has proven to be prolific but stubborn to release its treasures. The paleontologists, working in temperatures around minus 30 degrees Celsius, ran as many as five power tools at one time to dig out the fossils, including two electric jackhammer drills, a gasoline-powered jackhammer drill and two rock saws. Bad weather or poor visibility means a day of lost fieldwork because the team uses helicopters to travel to the site from the field camp near the Beardmore Glacier.

The cold and altitude are tough on people and equipment. Makovicky said he lost a half-day on the mountain trying to get the jackhammer to start in the extreme cold. He had to use the exhaust from a generator to warm it up.

“You’re thinking in ways that you’re not used to when you do fieldwork anywhere else,” he said.

It’s a mindset familiar to Hammer, who has made eight trips to Antarctica since the 1970s. The 61-year-old paleontologist mused it could be his last visit, at least to the Beardmore region.

“We have to get everything we can out now. There [probably] won’t be another camp here for 10 years at least,” Hammer said.

NSF-funded research in this story: William Hammer, Augustana College, Award No. 0837951; Peter Makovicky and Nathan Smith, Field Museum of Natural History, Award No. 0838925.

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Curator: Peter Rejcek, Antarctic Support Contract | NSF Official: Winifred Reuning, Division of Polar Programs